A phase II multicenter North American Brain Tumor Board Consortium trial to treat malignant astrocytomas with the combination of IV BCNU and oral temozolomide. The mechanism of denovo drug-resistance for these drugs is high levels of the enzyme O 6 alkylguanine transferase. BCNU will be used to deplete this enzyme with the theory that temozolomide will be more effective with lower cellular levels of the enzyme. There will be two patient groups studied 1.) recurrent glioblastoma after primary treatment failure (surgery, radiation and chemotherapy) and 2.) anaplastic gliomas and mixed anaplastic gliomas following surgery without prior radiation therapy.